1. Field of the Invention
This invention relates to a gas burner, more particularly to a gas burner which has several length-adjustable gas delivery pipes.
2. Description of the Related Art
A conventional gas burner includes an inner gas outlet member, an outer gas outlet member, a gas supply pipe unit equipped with two nozzles, an inner gas delivery pipe interposed between the gas supply pipe unit and the inner gas outlet member, and an outer gas delivery pipe interposed between the gas supply pipe unit and the outer gas outlet gas outlet member. In order to achieve effective mixture of combustible gas and enough air in the inner and outer gas delivery pipes, it is necessary for the inner and outer gas delivery pipes to have a ratio of length to diameter of about 6 to 10. The conventional gas burner suffers from the following disadvantages:
(1) Because only one outer gas delivery pipe is provided between the gas supply pipe unit and the outer gas outlet member of the conventional gas burner, the outer gas delivery pipe is relatively long, resulting in increased height of the burner head. PA1 (2) Air can access the spaces between the gas supply pipe unit and the inner gas delivery pipe and between the gas supply pipe unit and the outer gas delivery pipe through a relatively long air passage in the conventional gas burner, so the amount of air mixed with the combustible gas coming from the gas supply pipe unit is insufficient to gain a satisfactory burning effect. PA1 (3) The positions of the nozzles in the gas burner cause difficulties in adjusting or replacing the nozzles. In particular, the majority of the gas burner must be disassembled before adjusting or replacing the nozzles. PA1 (4) The amount of air needed to mix with different types of gas in the gas burner falls into three different ranges. Because the distances between the nozzles and the outer gas delivery pipes and between the nozzles and the inner gas delivery pipe are fixed, the conventional gas burner can be used with only one of liquefied petroleum gas, natural gas, or city gas.